Process of manufacture of half-tone printing-blocks.



PATENTED AUG. 25, 1908 W. & H. B. BELL. PROCESS OF MANUFACTURE OF HALE TONE PRZN'TI NG'BLUUKS APPLICATION IILBD DBO. 1,1906

WITNESSE Lbs K W- wwwn LL AND nanny n.- BELL-F MosMAN 1 1 ius'rlmtm.

rnoonss: or MANUFACTURE OF HALF-TONE PRINTING-BLOCKS.

To all 'wllom itma-g/ encer/1.; H

Be it known that'we, Wniumi BELL and HARRY BnYon BELL, suhjectsof the King of Great Britain andlrcland, and residents, respectively, of Redan street, M'osman, near Sydney, in theState of New South \Vales, Commonwealth of Australia, and (/owles Road, Mosman, near SydneyIaforesaid, have invented an Improved Process of Manufacture of Half-'lone Printing-Blocks,,of which the following a specification.

This invention. relates to. an improved manufacture of half tone printing blocks and has for its object the prodiu-tion of a block whose surface is formed in relief by the use of which the overlay or make ready for printing is almost if notentirely dispensed with. In the manufacture of such a block a smaller amount of skilled labor is'required in the fine etching than has heretofore beenfound necessary in. the production of blocks for a siniilarpurpose.

This invention main y consists in forming the printing surface of a blockin relief by subjecting it to a yielding pressure obtained by using a plastic sheet such as lead, leather, or gutta percha in a pressure press, the back of tho block having previously been prepared and weakened on certain predetermined parts corresponding to the high lights and halftones on the printed surface to permit of the of these weakened parts, or by subjecting to pressure a comparatively thin shell of and half' tones of the metal-upon whicha printhas been developed and lnn'n'ed in superposed upon a mold or die the-surfaceof which is formed with de pressions correspomling to the high lights superposed plate into which depressions the overlying portiohs of, the thin plate are forced.

In the carrying out of this invention the production of the printing block entails the treatment, in one instance, of both surfaces of the plate, in'another, of one-surface only of'two metal plates, and'inathird, the treat f metal ,plate and one gelatin.

ment of one I That surface which is' ultimately 'inting surfaceis hereinafter referred to as the face and the other which, printing is referred to ,flas theback. I

' The invention is illustrated in the accompanying'thnwing, wherein,

Figure l is a vertical sectional. view of I UNirEn .srifrrns r i Application filed D e'eexiiherl buckling or depressing n' ()FFIQ:

Letters Patent.

printing v etched; Fig. 2 1S aview illustrating the block with its etched back resting upon the jbed plate of a pressurezpress; Fig. 3 is a vertical sectional view of the block after both. its face and back havebeen treated according to the present invention F ig'. 4 is a view illus= trating the production of a printing blockfrom two sheets of metal of different thicknesses," and Fig. 5

production of a printing block from a sheet of metal and a gelatin sheet.

i In referring to the operation in which both surfaces of a plate are treated, a photo+ graphic negative of the object to be reproduced is taken in the ordinary-way through the usual lined, Levy, niezzograph, or other similarscreen.

thereon. By stripping onto a celluloid film is meant stripping the actual collodion film Patented Aug. 25, 1908. x

is a view illustrating the NEAR synnnn'unw souTnfWAtEs,

block showing the back thereof The negative is then stripped 1 onto a thin celluloid film and allowed to dr l'roni' its glass or other original support in a way well-knownto photographersor photoengravers. As this film is too delicate to be used alone as a negative it mustbe mounted upon a support, but as it is required to be printed through from either side in the sepa rate treatment of the. back and front sidesof the plate, the support used must be very thin, otherwise the light would be dispersed too much when the reinounted film is'used with sensitized face outward; A thin sheet of celluloid acts sullicientl as a mount. Accordingly, the collodion film which has been stripped from the original support used in the camera is squeegeed down into a thin sheet of transparent celluloid and allowed to dry thereon, and when dry the mounted film is thus used as'a negative. Theoretically, the eollodion film could be used without remounting on the celluloid mount, but such is not commercially practicable except in very rare cases. The metal plate l-'preferably production of the-block, is sensitized upon its back 2' with any of the well known sensitizing solutions, preferably fish glue and ammonia, and a bichromate of potash or print is then taken upon it from the celluloid mounted. filament by placing the celluloid -face thereof in contact with the sensitized surface of the metal in a printing frame and exposing it to light in the usual way. The back of the plate is then developed, namely, washed in water soaked in an anilin dye, thesoluble glue washed out and the i material. In this part of the operation very little skill is required to effect the correct etching.

The plate is withdrawn from the bath when the required depth. has been obtained. The face is sensitized and a print taken upon it from the same celluloid backed nega-'- tivc. In. this case, however,- the collodi'on film on. the celluloid mounting is, placed in contact with the face of the plate. Care must be exercised in the placing of the film on the face so as to insure .the accurately registering or coinciding of the prints on the back and front of the plate. The face is then developed, the print burned in and the plate while still hot is placed upon a hard metal slab 4 in a pressure press 5 with its deeply etched surfaceor back resting upon the slab and a sheet of lead 6 placed upon itsupper surface or face. Sufficient pressure is then applied through the lead sheet to cause the thinned or weakened portions to be forced downward to a degree corresponding to the amount of the weakening the plate has been subjected to at these parts; thus those portions which represent the high lights or whites and which have been most deeply etched, are forced down; ward the most, whereas those representing the half or middle tonesdo not sink so far, while those portions representing the darker shades or blacks do not compress. Should the plate be allowed to cool after the burning in process is completed it may be reheated to soften it prior to embossing it in the press. Should it be found inconvenient, however, to submit the plate to pressure while hot, this operation maybe carried out when it has cooled, in which case a sheet of gutta percha, leather or lead may be used to effect compression in the pressure press. Greater pressure, however, is required in this case. The face or printing surface of the plate when removed from the press presents an embossed surface. It is then subjected to the action of a mordant or acid bath toetch the face, the back meanwhile be ing protected by an acid resist. Owing to its embossed surface the plate requires com-- p'aratively little fine etching to produce a clean sharp printing surface, thus the time a; present employed to effect the fine etching of a half tone plateis reduced. The plate is now ready for proving and is mounted in the usualfin'a iiner.

To preduce thc bestv effects in printing i on one'surfaee only, directly from the co with a block made as above described a sof backing on the cylinder or platen of th printing machine may be dispensed with anda, hard backing substituted. It will also be found. that a printing block made as above described may be used with good results in a worn printing press where slackness of the working parts causes play. for the reason that the block does not require to registor with a make ready. Owing to the high lights being well beneath the surface they are protected largely from contact with the ink rollers thus minimizing the danger of clogging and so obviating frequent stoppages of the machine to allow for washing of the plate.

Although we have described the 'mbuntin'g of the negative on a thin sheet of c'elluloid and using both surfaces to obtain prints therefrom, it is obvious that the same result is obtainable by making two negatives, one

being reversed and the other not reversed. In

this case the eollodion surface of each is applied-t0 the sensitized surfaces of the metal. The fermer'procedure is preferable as it is less costly than .the latter. In the case in which two sheets of metal preferably of copper tively thick'and the other 1. comparatively thin.

Both are sensitized and printed u on dion film, which need not in this case-be stri' petl from its. backing as the film is in eaci case plated in contact with the sensitized face of each sheet of metal. prints are then 'leveloped and burned in in the usual manner. The thick plate. is then deeply etched in a similar manner to that descri bcd before, and on removal from the bath is coated with some suitable glue,

preferably with, a preparation known as Chatterton s Compound which consists of Stockholm tar -one part, resincne part, and gutta perchathree parts, by weight. The lighter'plate is then superposed u the heavier plate, with its printed sur ace uppermost, care being taken that theprints on both plates accurately register. The two plates are placed in a pressure press with a sheet 6 of lead, gutta percha, or leathersuperposed upon the printed surface,- of the thinner plate. Pressure is then applied.

Under the compressing action of the press those portions of the thin plate-which are unsupported by lying immediately above the deeply etched portions of the thick plate are forced downwards into these depressions, the depth of these indentations correspchiding to the varying depths of'the more or less deeply etched surface. two plates together. plate is etched and is then ready for place of using metal plate 1 The face of the thin the block is mounted and printing purposes. two sheets of metal a thin or zinc-are used, one 1 is eompara- The 1 The glue firmly holds the In v and a backing or die 1 con- 3 ention, and de- Letters Patent, is

producing an etched V e which consist :2) etching 'th ponding and register- (3) pressing the high li therein, (4) etching What we claim as our inv re to secure by The process of ne printing plat ng the face, through a print corre ing with the fa to sink the fa the etching on the bacl sisting of a Wash out gelatin relief e gelatin taki ng the plan his case the surf sheet of bichromatized half to ashed out in the The surface of y copper or zincand printed nd burned. plate it is su t; the back of n contact with surface of the gelasubmitted to preser or gutta percha e face of the On removal from ed and the metal t mounted as one 1 way with hot water.

is prepared by upon and the Upon the cool pon thegelatin shee late being placed i or relieved being sensitized rint developed a s cing an embossed plate which conthe back of 'ocess of produ tone printing ting the front gister from the one ne pressing the plat against a rig sists in prin e with a re- Hi back plate so into retching the fa whereof we have pecification silient follower as to bring the blacks lief, and finally e In testimony names to this's two subscribing witnesses. v

' WILLIAM BELL.

HARRY B. BELL.

sure, a sheet of lead, leat being placed between tl plate and the press. ess'the print is etch and the gelatin shee lock in the usual manner It is obvious that electro types taken from made accordii printing adva such blocks.

types or stereopi'lnting blocks ion possess the lg to this invent lc by the use of ntagos obtainab C. G. Herr 

